There has recently been made an intensive study on an organic thin-film light emitting device wherein light is emitted when electrons injected from a cathode and holes injected from an anode are recombined in an organic luminous body interposed between both electrodes. Intense interest has been shown toward this light emitting device because of such a feature that it is thin and enables high-luminance light emission under a low driving voltage and multicolor light emission by selection of an emissive material.
Since technology of enabling high-luminance light emission using an organic thin-film light emitting device was found by C. W. Tang et al. of Eastman Kodak Company, a lot of research organizations have studied this technology. A typical constitution of an organic thin-film light emitting device proposed by Eastman Kodak Company is that a diamine compound having hole transporting properties, an emissive layer made of tris(8-quinolinolate)aluminum(III) and a cathode made of a Mg—Ag alloy are sequentially formed on an ITO glass substrate, which enables green light emission of 1,000 cd/m2 at a driving voltage of about 10 V (see Non Patent Document 1).
Since the organic thin-film light emitting device enables various color light emissions by using various fluorescent materials as an emissive layer, a study on its practical use as a display has intensively been made. A most advanced study is a study on a green emissive material among emissive materials of three primary colors. At present, a study on a red emissive material and a blue emissive material has intensively made for the purpose of improving characteristics.
One of the largest problems in the organic thin-film light emitting device is to enhance durability of an element. With respect to a blue light emitting device, there are few blue emissive materials having excellent durability and high reliability. For example, blue light emitting devices using a pyrene compound substituted with an aryl group are disclosed (see Patent Documents 1 to 5). There is also disclosed an example using a pyrene compound having four carbazolyl groups (see Patent Document 6) in the blue light emitting device. However, any blue light emitting device is insufficient in durability.    Patent Document 1: Japanese Unexamined Patent Publication (Kokai) No. 2000-273056 (claims 1 to 2)    Patent Document 2: Japanese Unexamined Patent Publication (Kokai) No. 2002-63988 (claim 1)    Patent Document 3: WO2004/096945 pamphlet (patent claims)    Patent Document 4: Japanese Unexamined Patent Publication (Kokai) No. 2004-75567 (claims 1 to 4)    Patent Document 5: Japanese Unexamined Patent Publication (Kokai) No. 2004-139957 (claim 1)    Patent Document 6: Japanese Unexamined Patent Publication (Kokai) No. 2003-272864 (claim 1)    Non Patent Document 1: Applied Physics Letters, USA, 1987, Vol. 51, No. 12, pp. 913-915